[Zope] How do You guys manage integrity in Zope

i have made a few sites in Zope by now, and I often have problems with integrity in the database. Ie. with a structure like this: users user1 user2 user3 ... articles article1 article2 article3 If I have an author field in "article1" that is the id of "author2" and I then delete "author2" I get an error when trying to get the authors properties like e-mail, name etc. Off course I can test to see if the author exists before trying to pull out the data, but this seems like a messy way to do it. How do the rest of you guys solve this problem? Is zPatterns nessecary? regards Max M